We propose to continue our ongoing study of diet and cancer conducted in a cohort of 121,700 U.S. female registered nurses who have been followed with biennial questionnaires since 1976 and who are currently 47 to 72 years of age. Continued follow-up will permit assessment of lifestyle changes in this well characterized cohort of middle to older aged US women. Risk factors include, in addition to diet and post-menopausal hormones, physical activity, smoking, obesity (including waist to hip ratio), and reproductive factors. The dietary aspect of the study was begun in 1980 when the first semiquantitative food frequency questionnaire (SFFQ) was completed by approximately 89,000 women. An expanded version of the SFFQ was used in 1984, 1986 and 1990 and will be used in 1994 and 1998 to update diet. These data will provide exposure information both close in time to the diagnosis of cancer, which is likely to be important for a number of nutritional factors postulated to act in the later stages of carcinogenesis, and remote diet. With diet assessment repeated over 14 years of follow-up, we will examine change in diet in relation to cancer risk. Specific components of diet will be examined in relation to risk of breast, colon, lung, ovarian, and endometrial cancers, and melanoma. This proposed research will greatly strengthen our ability to test a wide variety of hypotheses relating dietary factors to the incidence of cancers. After 18 years of follow-up (assuming 90% power and an alpha error of 0.05) relative risks of 1.4, 1.4, 1.6, and l.16 for extreme quintiles of nutrient distributions can be detected for cancers of the breast, colon, lung, and melanoma respectively. A second major component of the study addresses relations between postmenopausal hormones and risk of cancer. Specific analyses will address type of hormone used. The analyses will assess the potential interaction between alcohol use and hormone replacement therapy on risk of breast cancer. In addition, risk benefit analyses will address life expectancy in relation to use of postmenopausal hormones and also moderate alcohol intake.